As is well known the turbine receiving the gas turbine engine's fluid working medium (gas path) is exposed to an extremely hot environment. There is an ongoing attempt in industry to improve the efficiency and performance of the gas turbine engine, which invariably increases the operating temperatures of the engine. To this end much effort over recent years has been directed to turbine cooling technology which has seen significant advances. Of course, it is abundantly important to maintain temperatures of the exposed metals to within tolerable limits. This invention is concerned with the platforms of the stator vanes in the turbine section and particularly to cooling the abutting edges of the platforms of the adjacent segments in the stator of the turbine. The platform is exposed to the gas path on one surface and to cooling air on the other surface. The cooling air is supplied thereto from the engine's compressor and serves to cool the engine's components.
One of the problems that has been persistent is that the edges of adjacent platform in each of the segments of the stator sees a large temperature difference on opposing surfaces. For benefits in performance it is also necessary to maintain minimum leakage of the cooling air between the edges of adjacent vane segments. These large thermals impose severe thermal stresses resulting in a durability problem of the vane. Typically feather seals are disposed between adjacent platforms. The platforms are formed integrally at the tips and roots of each vane, and the vanes are formed into segments defining the annular shaped stator. Each adjacent side edge of adjacent platforms in the segments are slotted to receive a feather seal. To avoid interference with the feather seal which is generally a flat, rectangular shaped, thin sheet metal member, the slots are oversized in both the axial and tangential directions. The opposing side edges of the feather seal fit into the opposing slots in adjacent segments and due to the oversize is capable of moving.
While there have been attempts to purge the side edges that are exposed to the gas temperature path temperature, such attempts were inadequate. The feather seal, for example would be perforated to allow coolant air to exist between the platform surfaces, but the oversized slot and consequential movement of the feather seal disrupted the flow of coolant and permitted the edges of the platform to overheat and owing to the high thermals durability problems would be evidenced.
We have found that by shaping the slots in such a manner so as to preclude the disturbance of the volume of cooling air passing therethrough regardless of the relative position of the feather seal the durability problem alluded to above will be eliminated or minimized.